Under this heading are classed all those conditions where there is either partial or complete loss of vision without any perceptible ocular lesions. The term Amblyopia is applied to those cases where there is but partial loss of vision, and Amaurosis where the loss of vision is complete. Formerly many cases of loss of vision from excessive use of alcohol and tobacco were classed under the heading of amblyopia, but in the advance of ophthalmological knowledge they have been found to be cases of inflammation of the optic nerve behind the eyeball and are now classed as cases of retro-bulbar neuritis. Hemianopsia, while also considered under this heading, perhaps should not be, because, while there is no perceptible lesion of the eye, the cause is known as due to some cerebral disease.
Amblyopia ex Anopsia.-Weak-sightedness from disuse results when a child with hitherto healthy eyes commences to squint, for in an-effort to overcome the annoyance of seeing double he learns to suppress by a mental act the image seen by the squinting eye. As a result of this suppression when followed for months and years, there takes a permanent change in the nervous function of the eye, which is manifested by more or less loss of vision, amblyopia ex anopsia. This condition is often associated with high degree of hypermetropia and astigmatism and will usually not excite attention until the child has entered into school life, and is probably due to the fact that, owing to the refractive error, distinct images have never been focused upon the retina. If, however, the condition is not detected until adult life, no improvement is to be expected.
Other cases of amblyopia ex anopsia are due to non-use of the visual function, owing to congenital opacities of the cornea or lens, from persistent pupillary membrane, or in cases of strabisr in early infancy. There is usually but one eye affected in these cases, and, when the vision is defective in both eyes, nystagmus is often present. Often by bandaging the good eye and thus compelling the squinting eye to perform the function of vision, even for half an hour each day, the development of amblyopia may be prevented. An existing amblyopia can sometimes be benefited by this procedure; but as it has to be followed out for a very long time it is apt to be neglected. Naumow St. Petersburger Medicinische Wochenschrift, No. 3, 1889. in an analysis of 47 cases of death of new-born infants, has found in 12 cases retinal oedema, retinal haemorrhages into the macula, choroidal haemorrhages and the beginning of choked disc. The changes were found especially in those who suffered difficult and instrumental delivery, and he believes that congenital amblyopia has its origin in these changes, which are caused by stasis in the vessels of the head.
Traumatic Amblyopia may occur from any severe injury to the head, from concussion of the spine or from a direct blow upon the eye. In some of these cases there may be a fracture of the skull or a haemorrhage along some part of the nerve, which is apt to produce a neuritis; and, having then inflammatory signs in the eye, should not come under the classification of amblyopia. The prognosis of these cases, while often favorable, should, as a rule, be guarded and dependent somewhat upon the severity of the injury.
Amblyopia from Lightning.-Cases of loss of vision from a stroke of lightning are usually accompanied by such lesions as burning of the skin, hair or cornea; ptosis is often present and contract is apt to follow. In some cases there may be a neuroretinitis, or, later atrophy of the nerve. These cases often have a greater loss of vision than can be accounted for by the recognizable changes in the eye, and hence can only be considered in part an amblyopia.
Amblyopia from Loss of Blood.-Loss of sight may take place after severe haemorrhage and may be accompanied by changes in the retina or nerve, yet in some cases may present no visible lesions. It has been seen after severe haemorrhages from various organs, lungs, stomach, uterus, bladder, etc. Both eyes are usually affected in the large majority of cases and in nearly one-half the loss of sight is permanent. Temporary blindness may occur from loss of blood, and is due to the lack of blood supply to the visual centers or to the retina, and in these cases more or less complete recovery may be expected.
Hysterical Amblyopia.-Hysterical blindness is more frequently found in young girls and women. It is usually temporary and unaccompanied by hysterical symptoms. The loss of vision is usually complete, and but one eye is generally affected. These patients will often be made to see by placing a perfectly plane glass in the form of spectacles before the eyes and the result is due to suggestion. There is usually a concentric contraction of the field of vision, hemianopsia and color blindness may result from hysteria, and we have seen other functional disturbances, such as ptosis, blepharospasm and strabismus in hysterical subjects.
Pretended Amblyopia (Malingering).-The pretense of blindness is not infrequently met with, and, as a rule, these subjects only claim more or less complete blindness in one eye. Simulated blindness may be practiced for various reasons, the most frequent, perhaps, being in the order to secure damages after some trivial injury, to excite sympathy, to secure pensions, etc. We have seen blindness claimed from the mere lodgment of a cinder in the cornea, which had been removed, leaving no trace of its location behind.
An exaggeration, of an existing defect of the vision is often claimed. In all cases where the amaurosis is claimed to exist in both eyes, its detection becomes extremely difficult and may often only be proven by careful watching of the subject without his knowledge. The action of the pupils may give some clue; if dilated and immovable, the use of a mydriatic may be suspected, for in dilation of the pupil in true blindness there may be some contraction for the stimulus of a bright light or upon convergence and there is apt, also, to be a shade more of dilation when the eyes are in a shadow. By bringing an object suddenly before the eyes in assumed blindness there may be the natural closure of the lids to prevent injury to the eye. Where the loss of sight is claimed to be in but one eye, there are several tests that may expose the deception. The test by causing diplopia is perhaps the simplest. In this a prism of eight or ten degrees is placed before the sound eye with its base up or down, and if the person on looking at lighted candle fifteen or twenty feet away acknowledges the double images, binocular vision is at once proven. The crossed diplopia test is made by holding a prism of ten degrees base outward before the pretended blind eye, and if it really sees the eye will rotate inward for the sake of single vision. Another test is made by using a strong convex glass before one eye and a plane glass before the other to read the Snellen test type at twenty feet, and, by a reversible frame, make the person use unconsciously his bad eye. Again by paralyzing the accommodation of the good eye, or by placing concave lens in front of this eye, and, if the patient can read, we know it is done with the affected eye. The stereoscope, Snelling’s colored type and various other methods are also useful in discovering an assumed blindness of one eye.
In all these tests caution should be taken that the patient does not suspect that you are trying to detect his dissembling. Rather let him infer that you are seeking to find the cause of his amaurosis.
Hemeralopia (Nyctalopia, Night-blindness).-This condition is found quite frequently without any recognizable lesions of the eye and must be considered as distinct from the night- blindness occurring as a symptom of retinitis pigmentosa and other lesions of the fundus. Hemeralopia is a functional complaint due to exposure to strong, brilliant lights, and is more prone to affect those whose systems have become greatly debilitated from the want of proper food. It prevails sometimes as endemic in certain countries, as in Russia, during their protracted fasts; it is frequently found in sailor, from exposure to tropical suns, and is often by them called “moon-blindness;” in soldiers, after prolonged marches; in travellers in the arctic zone and in those who work before furnaces. Hemeralopia is sometimes congenital and then remains unchanged during life.
Persons suffering from night-blindness are found have good vision during daylight, but, upon the approach of dusk, or when going into a moderately darkened room, the vision becomes greatly impaired. The field of vision is normal and the fundus shows no lesion. THe cause of the difficulty is probably a torpor of the retina, and, under favorable conditions, improvement may be expected.
TREATMENT.-As the general health is usually more or less impaired in hemeralopia, a generous diet must be ordered. Rest and protection of the eyes from bright light are first required; in severe cases it may be necessary to confine the patient to a dark room with a gradual return to ordinary daylight.
Professor of Ophthalmology in the College of the New York Ophthalmic Hospital; Surgeon to the New York Ophthalmic Hospital. Visiting Oculist to the Laura Franklin Free Hospital for Children; Ex-President American Homoeopathic Ophthalmological, Otological and Laryngological Society. First Vice-President American Institute of Homoeopathy : President Homoeopathic Medical Society of the State of New York ; Editor Homoeopathic Eye. Ear and Throat Journal : Associate Editor. Department of Ophthalmology, North American Journal of Homoeopathy, etc.